Pan in pan heater

ABSTRACT

A device for heating the contents of a container when in contact with a container, comprising a sealed outer package, an actuatable heat source in the outer package and an inner package inside the outer package and having an actuation agent therein with a seal keeping the actuation agent in the inner package until the seal is broken. The preferred actuable heat source is a mixture of calcium oxide and a zeolite and the preferred actuation agent is water. Most preferred is the presence of an exotherm delaying material coating on said calcium oxide such as polyethylene glycol.

FIELD OF THE INVENTION

This invention relates to a device for heating the contents of a container and for keeping it warm. More particularly, the invention relates to a self-contained heater device that allows the contents of a container to be heated in a second container.

BACKGROUND OF THE INVENTION

Often times, it is desirable to heat food and other items in a container such as a pan or pot at a location remote from a source of heat such as a stove or oven. Other times it is desirable to take warmed or hot food and other items from the place of heating to another location, such as a picnic, school or church basement, scout meeting and any of the myriad of events that do not meet or gather where heat is available. Sometimes the location is in a location where fire is not permitted, such as a class room or outdoors during the dry season.

One such self-contained warmer is disclosed in U.S. Patent Application Publication No. US 2007/0034202, to Punphrey et al. in which a container with an exothermic composition is used to heat a vessel. A membrane is used to cover the exothermic composition, which is then activated by removal of the membrane. Various compositions are disclosed that are based on iron oxidation chemistry. The heater is in direct contact with the container and must be put on a heat-resistant surface to be used without damage.

U.S. Pat. No. 6,705,309 discloses a self-heating or self-cooling container in which tubular walls defining an internal cavity into which steam or hot air is placed as a source of heat. This, of course, requires a source of that heated material.

It would be a great advantage if a way of heating containers could be developed that have a controlled release of heat that is within acceptable safety limits.

Another advantage would be to provide a way of heating containers that produces heat over an extended period of time, rather than simply having an exothermic reaction that lasts a few minutes or less.

Yet another advantage would be to provide a way to generate heat by an exothermic reaction without having to wait for an activation agent to make its way to all the reaction components.

Other advantages will appear hereinafter.

SUMMARY OF THE INVENTION

It has now been discovered that the above and other objects of the present invention may be accomplished in the following manner. The unique aspect of this invention is that a controlled, dispersed exothermic reaction can be used to heat or cook the contents of a container quickly and effectively while maintaining the heat for an extended period of time. The device includes a sealed outer package with an actuatable heat source in the outer package and an inner package inside the outer package that has an actuation agent therein with a seal keeping the actuation agent in the inner package until the seal is broken. The preferred actuable heat source is a mixture of calcined calcium oxide and a zeolite and the preferred actuation agent is water. Most preferred is the presence of an exotherm delaying material coating on said calcium oxide such as polyethylene glycol.

The device is used to cook or heat the contents of a container, such as a pan or pot, by placing the device on one side of the container, preferably on the bottom. Also preferred is the use of an outer container that is large enough to hold the first container and position the heating device against the first container.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention, reference is hereby made to the drawings, in which:

FIG. 1 is a perspective view of the heating element of the invention; and

FIG. 2 is a perspective view of the device with containers using the embodiment shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIG. 1, the device of this invention, 10 generally, comprises a heat generating element 11 which has an outer pouch 17, an inner pouch 21 and a seal 25 that allows the contents of the two pouches to be mixed, thus generating an exothermic reaction to produce heat. The heat generating element 11 is shown in FIG. 2 as being located between a first or top pan 13, which contains food, liquids or other contents to be heated or kept warm, and a bottom pan 15. which isolates the heat from the surface on which the device is placed while heating. It is intended that any container can be used, as long as it is heat resistant to above the maximum temperature that the heat generating element can reach.

Preferred is an outer pouch 17 made from Aclar®, which is a polychlorotrifluoroethylene (PCTFE) material manufactured and sold by Honeywell International Inc. Aclar film is crystal clear, biochemically inert, chemical-resistant, nonflammable, and plasticizer- and stabilizer-free. Aclar laminates provide a wide range of gauges and thus barrier levels to allow flexibility in selecting the optimum barrier level for the chemical system chosen. Other similar pouch materials may be used as well. All that is required is that the material have a functional moisture and vapor barrier for the other components of the invention.

Pouch 21 has a frangible seal 25 that is preferably broken at the appropriate time by flexing or bending the package 11 to cause the activating agent in pouch 21 to mix with the heat generating material in pouch 17 and exotherm in outer pouch 17. In a preferred embodiment, pouch 17 may have a vacuum in the outer pouch to increase the rate of flow of water to all regions of the pouch, causing uniform time of reaction. The amount of vacuum can range from about 8 psi to about 13 psi, with about 11 psi being preferred.

There are a number of combinations of heat generating materials and activating agents that are suitable for use in the present invention. The selection of specific components is to be based upon cost, compatibility, ease of control of the exotherm, and other factors. Also contemplated is the use of a coating agent to retard the rate of exotherm to prolong the time which the contents of the container remain warm or hot.

The preferred activating material of this invention is water. This is plentiful and safe, and reacts with a number of materials to produce an exothermic reaction.

The preferred heat generating material is a crystal formed from several components that, when free from moisture, are stable for up to three to five years or more, and which react when moisture is present to generate heat. The preferred crystal is made from crystalline calcium oxide. The weight of the heat generating material to the volume of actuation agent ranges from about 1:2 to about 1:1, and preferably about 3:4. In the most preferred mixture of the heat generating material is a mixture of calcium oxide with a zeolite powder. Preferred is a ratio of calcium oxide to powdered zeolite of about 20 to 40 for calcium oxide and from about 4 to 8 for powdered zeolite. Most preferred is a ratio of calcium oxide to powdered zeolite is 30-35:6-7 and the ratio of the solids to the volume of water is about 3:4.

As noted above, the heat generation material most preferred, using the above components includes a calcined calcium oxide. This material is available as a small article size, with a diameter less than about 0.2 mm, and as a particle of somewhere between 0.2 and 0.8 mm. Larger particles are ground and smaller ones sieved, and the calcium oxide is then calcined. It has been found to be effective to calcine for at least 60 to 120 minutes, and preferably about 90 minutes, at temperatures above 500° C., and most preferably at about 550° C. for that period of time. The calcined calcium oxide is, of course, desiccated to prevent any contamination by moisture. Powdered zeolite are mixed with the calcium oxide in moisture free conditions, in an appropriate reaction ratio to provide the exothermic reaction upon contact by the activating agent water.

In a preferred embodiment, the heat generation material also includes a small quantity of polyalkyl glycol such as polyethylene glycol or similar materials which is used to coat the calcium oxide prior to initiating the exothermic reaction. This small coating, of 1% to 7% polyethylene glycol by weight in the total composition slows down the reaction with water to prolong the heat for over two hours. A preferred weight percent of polyethylene glycol is from 3% to 4%. Tests have been made that have maintained a container of one liter of water at a temperature of 140° F. to 165° F. for more than two hours and in some instances up to eight hours, thus allowing the goods in the container to remain hot for much longer times than previously possible. Thus, for example, at a gathering, food can be kept warm while people arrive over an extended period of time.

While particular embodiments of the present invention have been illustrated and described, it is not intended to limit the invention to any specific embodiment. The description of the invention is not intended to limit the invention. 

1. A device for heating a container, comprising: a sealed outer package; an actuatable heat source in said outer package; an inner package inside said outer package and having an actuation agent therein and a seal keeping said actuation agent in said inner package; and whereby heat is generated upon activation by said actuation agent upon breaking said seal keeping said actuation agent in said inner package.
 2. The device of claim 1, wherein said actuable heat source in said outer package is a mixture of calcium oxide and a zeolite.
 3. The device of claim 2, wherein the ratio of calcium oxide to powdered zeolite is about 20 to 40 for calcium oxide and from about 4 to 8 for powdered zeolite.
 4. The device of claim 3, wherein said ratio of calcium oxide to powdered zeolite is 30-35 to 6-7.
 5. The device of claim 2, wherein said actuation agent is water and the weight of the heat generating material to the volume of actuation agent ranges from about 1:2 to about 1:1.
 6. The device of claim 2, wherein said actuable heat source further includes a quantity of exotherm delaying material coating said heat source to slow down the penetration of said actuation agent.
 7. The device of claim 6, wherein said exotherm delaying material as a polyalkyl glycol.
 8. The device of claim 7, wherein said polyalkyl glycol is polyethylene glycol.
 9. The device of claim 1, which further includes a vacuum in said outer package sufficient to increase movement of said actuation agent into said outer package when said seal is broken.
 10. The device of claim 1, which further includes an upper container for holding contents to be heated and a lower container for holding said device against said upper container.
 11. A device for heating a container, comprising: a sealed outer package; an actuatable heat source means in said outer package for generating heat; an inner package inside said outer package and having an actuation agent means therein for activating said heat source means and a seal means for keeping said actuation agent in said inner package; and whereby heat is generated upon activation by said actuation agent means upon breaking said seal means keeping said actuation agent means in said inner package.
 12. The device of claim 11, wherein said actuable heat source means in said outer package is a mixture of calcium oxide and a zeolite.
 13. The device of claim 12, wherein the ratio of calcium oxide to powdered zeolite is about 20 to 40 for calcium oxide and from about 4 to 8 for powdered zeolite.
 14. The device of claim 13, wherein said ratio of calcium oxide to powdered zeolite is 30-35 to 6-7.
 15. The device of claim 12, wherein said actuation agent means is water and the weight of the heat generating material means to the volume of actuation agent ranges from about 1:2 to about 1:1.
 16. The device of claim 2, wherein said actuable heat source means further includes a quantity of exotherm delaying material coating said heat source to slow down the penetration of said actuation agent.
 17. The device of claim 6, wherein said exotherm delaying material as a polyalkyl glycol.
 18. The device of claim 7, wherein said polyalkyl glycol is polyethylene glycol.
 19. The device of claim 11, which further includes a vacuum in said outer package sufficient to increase movement of said actuation agent means into said outer package when said seal means is broken.
 20. The device of claim 11, which further includes an upper container for holding contents to be heated and a lower container for holding said device against said upper container. 